The occurrence of arterial dissection associated with percutaneous excimer laser coronary angioplasty (PELCA) is a significant technical consideration that may limit medical applications. By developing a system of sequential fiber inactivation for fiber optic catheters, in which only a portion of the fiber optics carry energy at any one time, arterial dissection may be reduced by obtaining the same biological effects from less energy per laser pulse. This process is referred to as multiplexing. The long-term objectives are to modify our existing commercial laser (already in use for PELCA), develop the processes to manufacture catheters for multiplexing, and conduct animal and clinical trials to validate results of Phase I in vitro testing. The primary basis for technical innovation is in reducing acute complications of PELCA. This should allow more aggressive artery debulking, producing a larger lumen, and attacking even more difficult lesions, allowing an expansion of indications into areas currently limited by the complication rate. Once acute success is improved and larger lumens are created, we may see reductions in the restenosis rate. Reduction in ablation trauma may also make this laser a better clinical tool in other medical applications such as ophthalmology, otolaryngology and orthopedics.